1. Field of the Invention
The present invention relates to a gel-forming silicone composition with low modulus of elasticity for use in protecting electrical and electronic components, and to a cured product of the same.
2. Description of the Prior Art
Silicone gels are known as cured silicone products which have so-called "rubber hardness" values of 0 because of their extremely low crosslink density, as contrasted to other cured silicone compositions such as elastomers and resins.
Silicone gels, with their excellent electrical insulation properties as well as stability of electrical characteristics and flexibility, are used as potting or encapsulating materials for electrical and electronic component parts, particularly as coating materials for protecting control circuit components such as power transistors, IC's, capacitors and the like from thermal and mechanical disorders.
As a material for forming a silicone gel, there have been known a variety of addition-curable type organopolysiloxane compositions, including, for example, those which comprise an organopolysiloxane containing a silicon-bonded vinyl group and an organohydrogenpolysiloxane containing a silicon-bonded hydrogen atom wherein the amount of the silicon-bonded hydrogen atoms relative to the amount of the silicon-bonded vinyl groups is reduced to a very low level, i.e. about 0.3 to 0.6 silicon-bonded hydrogen atoms per silicon-bonded vinyl group, and those which comprise an organopolysiloxane containing a statistical average of from 0.1 to 2 vinyl groups per molecule (Refer to Japanese Pre-examination Patent Publication (KOKAI) Nos. 56-143241, 62-039658, 62-039659, 63-035655, and 63-033475.).
However, with the progress in electrical and electronic component parts and the trend toward higher power and miniaturization in recent years, the silicone gel used for protection of the component parts has come to suffer a thermal stress arising, for example, from the heat generated by the circuit components themselves, variations in environmental conditions under which the component parts are used, and so forth. The thermal stress generated in the silicone gel would lead to breakage of semiconductor device or the like.
This problem is due to the fact that the conventional silicone gels used for the above purpose have high moduli of elasticity and, hence, produce stresses at the areas of contact with the circuit components.